442 Immune checkpoint inhibitors potency assay using in vitro expanded TILs

<h3>Background</h3> Tumor-infiltrating lymphocytes (TILs) are immune cells that have migrated from the bloodstream into a tumor. These lymphocytes play a crucial role in the body’s immune response against cancer and their behavior and function are influenced by the tumor microenvironment (TME), which includes various factors such as cytokines, chemokines, and immune checkpoint (IC) molecules. TIL therapy represents a promising avenue in oncology for harnessing the immune system to target and eliminate cancer cells. It can be combined with other immunotherapies (IO) or conventional cancer treatments to enhance its effectiveness. The combination of TIL therapy with IC inhibitors represents a promising strategy in cancer IO, offering the potential for enhanced anti-tumor immunity, improved response rates, and broader applicability across various cancer types. <h3>Methods</h3> Expanded TILs were produced from 8 tumor tissue across 6 different tumor types (melanoma, uterine sarcoma, colorectal, lung, ovarian and renal cell carcinomas) according to standard protocols.¹ TILs phenotype and IC expression was measured by flow cytometry (FCM) before and after 21 days of expansion. The tumor killing potency was evaluated incubating TILs at 8 effector-target (E-T) ratios with 3 different solid tumor cell lines (melanoma, A375, lung carcinoma A549 and ovarian carcinoma OVCAR-3) in presence of IC inhibitors, for 24 hours. Tumor killing potential was calculated according to controls without effector cells. Those results were confirmed when TILs were incubated with patient-derived autologous tumor cells using Vivia’s 3D TME-Aligned model. <h3>Results</h3> TILs from different indication expanded between 9 to 900-fold over 21 days, IC as TIM3 expression increased in 7 from 8 samples after expansion, exhaustion markers kept stable while senescence markers slightly increased. Regarding killing potency, TILs were able to kill up to 90% of tumor cells in 24h, in a E-T ratio-dependent way. Using a minor effective E-T ratio, 1:1, the addition of a pool of IC inhibitors, including TIM3, Lag3, PD1, NKG2A, TIGIT, CTLA4 inhibitors (5µg/ml), improved 22% of tumor killing potency. <h3>Conclusions</h3> <i>In vitro</i> expanded TILs demonstrated to be a useful tool for the study of new and personalized therapies. Cells obtained from different donors demonstrated different killing potency against tumor cells, combined IC inhibitors significantly improved TILs anti-tumor potency. Those assays could also help to better understand the mechanisms of immune response to tumors, identify new tumor antigens, and development of new IO strategies. <h3>Acknowledgements</h3> We thank Vivia laboratory team for their commitment. We also want to particularly acknowledge the patients, the Biobank HGUE (B.0000847) integrated in the Valencian Biobanking Network, the Biobank MD Anderson Foundation (B.0000745) integrated in the Spanish National Biobanks Network, and the Biobank Hospital Ramón y Cajal-IRYCIS (B.0000678) integrated in the Biobanks and Biomodels Platform of the ISCIII, for its collaboration. <h3>Reference</h3> Jin, <i>et al. J Immunother</i> 2012;<b>35</b>:283–292. <h3>Ethics Approval</h3> All patient samples were collected under patient consent and approved by local ethical committees. <h3>Consent</h3> Written informed consent was obtained from all the authors for the publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.